Method of squeeze cementing in cased boreholes



Sept. 20, 1955 ALLEN ETAL 2,718,264

METHOD OF SQUEEZE CEMENTING IN CASED BOREHOLES Filed July 25, 1951 5 5 1/ z 5;? S/ I 1' E I I E- r i SURFACE CASING :5 SURFACE ens/us i 1 ,PRIMARY CEMENT on. STRATA on. rrun A TER STRA TA ATER STRATA ORIGINAL ZONE ORIGINAL ZONE FIG. I. FIG.2.

INVENTOR. Thomas 0. Allen y John C. McDuffie Jr.,

United States Patent 0 METHOD OF SQUEEZE CEMENTING IN CASED BOREHOLES Thomas 0. Allen and John C. McDuflie, Jr., Houston, Tex., assiguors, by mesne assignments, to Esse Research and Engineering Company, Elizabeth, N. J., a corporation of Delaware Application July 25, 1951, Serial No. 238,538

6 Claims. (Cl. 166-23) The present invention is directed to a method of squeeze cementing. More particularly, the invention is directed to a method for squeeze cementing in cased well bores.

In the completion of oil and gas wells, it is sometimes necessary to isolate undesirable fluids such as mud, gas, or salt water from the intended completion interval; This is accomplished by perforating the casing and subsequently squeezing sealing material into and through the perforations in order to form a pancake or sheat of impermeable sealing material concentrically around the well bore. Such a pancake orsheath prevents vertical migration' of fluids and thus can be used to isolate undesirable gas or water from the producing interval. These operations are commonly referred to as precautionary squeeze jobs and they are performed in cases where faulty primary cement jobs are believed to exist as well as in cases where no cement sheath is present opposite the interval where isolation is desired.

The present invention may be briefly described as involving a method for squeeze cementing in which an upper zone in a cased well bore is isolated from a lower zone therein such as by setting a plug between theupper zone and the lower zone. For example, the casing passing through a water strata may have the interior thereof isolated from the part of the casing below the water strata. The upper zone then has a body of fluid cementitious material located therein adjacent a formation to be squeezed. I

A shaped charge is then discharged laterally in the cementitious material against the casing to form perforations therein. Discharge of the shaped charge, besides forming perforations in the casing, generates a high pressure shock wave which nearly simultaneously results in cementitious material from the body thereof being forced through the perforations and into the strata to be squeezed. Thereafter, the excess cementitious material may be removed from the well casing by circulation or by drilling out.

The cementitious materials contemplated for use in the present invention include the hydraulic cements. The hydraulic cements may include the normal Portland cements, slow setting cements, and anhydrous gypsum cements.

The use of a shaped charge is well known and a high explosive of any type maybe used therein. Suitable high explosives such as pentolite, tetryl,T.N.T., R.D.X., and otherwell known high explosives may be used. The high explosives may be augmented by any suitably chosen booster explosive material. For example, tetryl may be used as a suitable booster for pentolite since tetryl is more sensitive to shock than is pentolite. The shaped charge is well known but employs a cone shaped cavity, with the base open, in the high explosive. shaped charge is suitably formed by employing a conical shaped wall to confine the lower portion of the high explosive. The conical wall member may be constructed of a suitable metallic material which may be a ferrous The cone r Patented Sept. 20, 1 955 fi ice charges are well known and details of the jetting exploding action thereof need not be given here since a discussion thereof will be found in the copious literature on the subject.

The invention will be further illustrated by reference to the drawing in which v I Fig. 1 illustrates a mode of the present invention'show ing a jet gun perforator arranged in a body of fluid cementitious material in a well bore; and

Fig. 2 shows the same well bore after discharging the gun perforator therein.

Referring now to the drawing, numeral 11 designates the earths surface in which a surface casing'12ihas been set. Arranged in the surface casing 12 is oilstringcasing 13 which penetrates an original zone 14? and .is cemented in place by cement 15. Above the originaljz'one 14 are formations 16, 17, 18, 19, and 20. Formations 16 and 17 are of shaley structure While formation 18 includes a water strata which is to be isolated so that production may be obtained from formation 19 includ ing an oil sand. The formation 20 may include sedimentary material.

A bridge plug 21 is set in the oil string casing at a point below the point where it is desired to perform the squeeze cementing job. A body of fluid cementious material is then located in the oil string casing adjacent the forma tlon to be squeezed. The portion of the oil stringc'asing above the plug 21 may be designated .asan upper zone while that below it may be designated as a lower zone. In the upper zone will be arranged a body of fluid cementitious material 22 as shown which may be a Portland cement. This body of cement is employed in excess of that required for the sealing or squeeze cementing job. After the fluid cementitious material has been located in the well casing adjacent the formation to be squeezed, a jet gun perforator 23 embodying a plurality of shaped charges 24 is lowered therein on a wire line or. electrical cable 25 suspended from the well surface 11 or a point thereabove. The oil string casing 13 contains a body of a fluid media 30 above the body of cementitious material 22. Referring now to Fig. 2, the condition of the well shown after the shaped charges 24 and jet gun perforator 23 have been discharged. It is to be noted that the level of the body of cement 22 has been lowered in the well casing 13 and that a substantial amount'of the cement has been forced out of the well casing'through perforations 26 resulting from the jetting exploding action of the shaped charges. By virtue of exploding the shapedcharges laterally in the well casing, the casing is perforated and nearly simultaneously the fluid cementitious material is forced out into the formation to form pancakes 27 and a sheath 28 around the casing 13 iso lating the water strata 18 from the oil sand 19. The casing traversing the oil sand 19 may then be perforated, as is well known, to allow production therefrom.

It will be seen from the foregoing description taken with the drawing that perforating with shaped charges in a body of fluid cementitious material results in practically simultaneously squeeze cementing. In short, the cement follows the high temperature jet stream which is cutting through the wall of the casing and 'is forced therethrough by a high pressure shock wave generated by the explosive.

It is believed that the beneficial effects of the present invention result from the generation of high pressure gases which force the cements into perforations which simultaneously 'dehydrates the cement slurry, causing nearly instantaneous setting of the cement'in the-pancakes 27 and the sheath 28. The impact pressureapplied from an explosive detonation is much greater1than1he or a non-ferrous metal. The function and use of shaped 535 sustained hydraulic pressure which may be safelyapplied in conventional squeezing. As a result, the cement which isset nearly instantaneously provides a positive seal when the explosive squeezing technique of the present invention is employed. Because the method of our invention causes an impact load rather than a sustained load on a well casing higher pressures can be safely applied than ordinarily used for squeezing without danger of failure to the casing from overloading.

Instantaneous dehydration and setting of cement is advantageous because operations may be continuous whereas in the conventional techniques wherein the easing is perforated and then squeeze cemented, some 12 to 24 hours shutdown is necessary while waiting for the cement to set. In the present invention the excess fluid cement in the well casing may be circulated out immediately and the other operations normal to well production and the'like may be commenced.

"While the present invention has been described and illustrated by the employment of the shaped charge to generate a shock wave or a body of high pressure gases in the cementitious material, modifications thereof are intended to fall within the spirit and scope of our invention. For example, it may be possible to form perforations by gun perforating, using a bullet or a shaped charge, and simultaneously exploding in the cement a high explosive to generate a high pressure shock wave and/ or gases therein. It is contemplated that our invention is also applicable to exploding a series of high explosive charges to generate a plurality of shock waves in'the cement to cause squeeze cementing as has been described.

In the description taken with the drawing, the body of cement is shown arranged adjacent a formation to be sealed with the cement arranged in an isolated upper zone, the upper zone being isolated from a lower zone by setting a plug. It is contemplated that our invention is not to be limited to usage where an upper zone is isolated from a lower zone. It is contemplated that the cement may be located adjacent a formation to be squeezed or cemented and the present invention practiced without the step of setting a plug to isolate one zone from another. For example, it is possible, in accordance with our invention, to locate the cement at the bottom of the hole and to squeeze the cement into the formation by discharging a high explosive which will cause perforations in the casing and squeezing of the cement. This may also be achieved by allowing cement to set in the casing to fill effectively the lower part of the casing which has penetrated zones no longer in production and then to arrange a body of fluid cementitious material above the cemented portion in the casing.

It is contemplated that our invention not be limited to the particular illustration taken with the drawing. For example, it is not uncommon that an oil-water interface exist in a producing sand. Therefore, in the practice of our invention it would be desirable to perform a squeeze job to seal off that portion of the producing formation which contains water from the other portion which contains oil. Likewise, when a producing sand overlies a shaley structure which, in turn, overl es a water sand, it will be desirable to perform the cementing job in the shaley structure below the producing sand but above the formation where water is encountered.

Our invention is intended to be applicable to all situations encountered in a well bore where it is desirable to isolate a producing formation containing oil, gas or other valuable fluids from fluids which it is desired to exclude from the well bore.

{The nature and objects of the present invention having been completely described and illustrated, what we wish to claim as new and useful and to secure by Letters Batent is:

l :1. A method for. precautionary squeeze cementing in a'-well,: casing sheathed in cement and traversing a formation to be squeeze cemented which comprises isolating an upper zone in a cased well bore from a lower zone there'- in, locating a body of fluid cementitious material in said isolated zone adjacent said formation to be squeezed, discharging a high explosive shaped charge in said cementitious material against the casing to form perforations in said casing, cement sheath, and formation, substantially simultaneously forcing only a portion of the cementitious material through the perforations by the effect of said discharge, and then immediately removing a remaining portion of fluid cementitious material from the well casing.

2. A method for precautionary squeeze cementing in a well casing sheathed in cement and traversing a formation to be squeeze cemented which comprises isolating an upper zone in a cased well bore from a lower zone therein, locating a body of fluid cementitious material in said isolated zone adjacent said formation to be squeezed in an amount substantially in excess of that required for the squeeze cementing, discharging a high explosive shaped charge in said cementitious material against the casing to form perforations in said casing, cement sheath, and formation and substantially simultaneously forcing only a portion of the cementitious material through the perforations by the effect of said discharge, and then immediately removing excess fluid cementitious material from said well casing by circulation.

3. A method for precautionary squeeze cementing in a well casing sheathed in cement and traversing a formation to be squeeze cemented which comprises isolating one zone in a cased well bore from another zone therein, locating a body of fluid cementitious material in said isolated zone adjacent said formation to be squeezed, discharging a high explosive shaped charge in said cementitious material against the casing to form perforations in said casing, cement sheath, and formation, forcing a portion of the cementitious material through the perforations by the effect of said discharge, and then immediately removing excess fluid cementitious material from said well casing, before it has set, by circulation.

4. A method for precautionary squeeze cementing in a well casing sheathed in cement and traversing a formation to be squeeze cemented which comprises isolating one zone in a cased well bore from another zone therein, locating a body of fluid hydraulic cement in said isolated zone adjacent a formation to be squeezed in an amount substantially in excess of that required for the squeeze cementing, discharging a high explosive shaped charge in said hydraulic cement against the casing to form perforations in said casing, cement sheath, and formation, substantially simultaneously forcing hydraulic cement through the perforations by the effect of said discharge, and removing excess fluid hydraulic cement from said well casing, before it has set, by circulation.

5. A method for precautionary squeeze cementing in a well casing sheathed in cement and traversing a formation to be squeeze cemented which comprises setting a plug in said casing to isolate an upper zone from a lower zone therein, locating a body of fluid hydraulic cement in said isolated upper zone adjacent said formation to be squeezed in an amount substantially in excess of that required for the squeeze cementing below a body of a fluid mediasubstantially filling said casing above the plug, discharging a high explosive shaped charge in said hydraulic cement against the casing to form perforations in said casing, cement sheath, and formation and to generate at least a high pressure shock wave in said body, squeezing a portion of the cement through said perforations by the effect of said high pressure shock wave, and then removing excess fluid cement from said well casing by circulation.

6. A method for precautionary squeeze cementing in a well casing sheathed in cement and traversing a formation to be squeeze cemented which comprises setting a plug in said casing to isolate an upper zone from a lower zone therein, locating a body of fluid hydraulic cement in said isolated upper zone adjacent said formation to be squeezed in an amount substantially in excess of that required for the squeeze cementing below a body of a fluid media substantially filling said casing above the plug, discharging a high explosive shaped charge in said hydraulic cement against the casing to form perforations in said casing, cement sheath, and formation and to generate at least a high pressure shock wave in said body, squeezing only a portion of the cement through said perforations by the eifect of said high pressure shock wave, and then immediately removing excess fluid cement from said well casing by circulation.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Lane Wells Gun Perforator Applications, No. 8, 

1. A METHOD FOR PRECAUTIONARY SQUEEZE CEMENTING IN A WELL CASING SHEATHED IN CEMENT AND TRAVERSING A FORMATION TO BE SQUEEZE COMENTED WHICH COMPRISES ISOLATING AN UPPER ZONE IN A CASED WELL BORE FROM A LOWER ZONE THEREIN, LOCATING A BODY OF FLUID CEMENTITOUS MATERIAL IN SAID ISOLATED ZONE ADJACENT SAID FORMATION TO BE SQUEEZED, DISCHARGING A HIGH EXPLOSIVE SHAPED CHARGE IN SAID CEMENTITIONS MATERIAL AGAINST THE CASING TO FORM PERFORATIONS IN SAID CASING, CEMENT SHEATH, AND FORMATION, SUBSTANTIALLY SIMULTANEOUSLY FORCING ONLY A PORTION OF THE CENMENTITIOUS MATERIAL THROUGH THE PERFORATIONS BY THE 